System and Method for Lining an Earthen Formation

ABSTRACT

A method of lining an earthen formation pit includes covering at least a portion of the pit with a polymer. A portion of the polymer-covered area may be additionally covered with bentonite. The bentonite and polymer combine, when hydrated, to form a layer that is substantially water impermeable. A portion of the formation may be covered by a protective slurry of water and cement. A portion of the formation may be covered by a water-resistant layer such as, for example, a plastic tarpaulin.

TECHNICAL FIELD

Embodiments of the invention relate generally to the treatment of earthen formations and, more particularly, to a system and method for lining an earthen pit.

BACKGROUND

Earthen pits are used in the drilling of geological formations to hold, for example, fluids used in the fracturing of such formations. When drilling, the fluids held in the earthen pits may be pumped at high pressure into the geological formation in order to create a channel further into the formation. In order to maintain an earthen pit for use during drilling, it is desirable to prevent the surfaces of the pit from eroding under the fluid pressure. Additionally, when earthen pits are formed in porous, sandy, or rocky material, it is desirable to seal the pits in order to prevent fluids from seeping into the Earth.

SUMMARY

In one embodiment of the invention, a method of lining an earthen pit includes covering at least a portion of the pit with a polymer and applying bentonite to at least a portion of the polymer-covered portion. The bentonite is adapted to combine with the polymer, when hydrated, to form a layer that is substantially impermeable to water.

Embodiments of the invention may provide a number of technical advantages. Embodiments of the invention may include all, some, or none of these advantages. In one embodiment, a method is utilized to line an earthen pit, either for short-term or long-term use. The method may include the use of a protective slurry to further the erosion-reducing capabilities of the polymer and bentonite clay layers. Such a method may be more effective at preventing erosion and fluid leakage in soils that do not have a high clay content.

Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and for further features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is an elevation view illustrating a system and method for lining an earthen pit according to an embodiment of the invention;

FIG. 2 is an elevation view illustrating a system and method for lining an earthen pit lining according to an embodiment of the invention; and

FIG. 3 is an elevation view illustrating a system and method for lining an earthen pit according to an embodiment of the invention.

DETAILED DESCRIPTION

Example embodiments and their advantages are best understood by referring now to FIGS. 1 through 3 of the drawings.

FIGS. 1 through 3 are elevation views illustrating a system 100 for lining an earthen pit 102 according to an embodiment of the invention. In the illustrated embodiment, earthen pit 102 is a drilling reserve pit that is used for storing fluids from the drilling of a wellbore (not illustrated). However, earthen pit 102 may be any suitable earthen pit, such as an earthen livestock tank or an earthen pond. Earthen pit 102 may have any suitable size and shape. As one example, earthen pit 102 may be generally of a square shape one hundred feet in width, one hundred feet in length, five to ten feet in depth, and walls sloping at an angle of about forty-five degrees. As described in greater detail below, the lining of the earthen pit prevents, among other things, erosion of the pit's surfaces and leakage of the stored fluids into the subsurface of earthen pit 102 and the surrounding environment.

In the embodiment illustrated in FIG. 1, system 100 includes a user 104 utilizing an application device 106 to apply a polymer 108 to a surface 110 of an earthen pit 102. The present invention contemplates more, fewer, or different components for system 100 than those illustrated in FIG. 1.

User 104 may be any suitable person, robot, or machine that utilizes application device 106 to apply polymer 108 to surface 110. Application device 106, in a preferred embodiment, is a mechanized applicator capable of applying polymer 108. Application device 106 may be other suitable devices for applying polymer 108 to surface 110. In at least one embodiment, polymer 108 is provided in dry, granular form and is applied with a mechanical, broadcast spreader.

User 104 may apply polymer 108 at any suitable amount. For example, polymer 108 may be applied to surface 110 at an amount of at least approximately one-tenth of a pound of polymer 108 per square foot of surface 110 to be covered. In a more particular embodiment of the invention, polymer 108 is applied to surface 110 at a depth of between approximately one-tenth and approximately two-tenths of a pound of polymer 108 per square foot of surface 110 to be covered.

The application of polymer 108 to surface 110 may be performed in any suitable manner. For example, in the illustrated embodiment, user 104 applies polymer 108 to cover all interior surfaces 110 of earthen pit 102. Any suitable dispersion of polymer 108 is contemplated by the present invention; however, in a preferred embodiment, at least the bottom 114 of earthen pit 102 is covered. In one embodiment, polymer 108 is applied to bottom portion 114 and to lower wall portion 116. Polymer 108 is any suitable polymer adapted to combine with bentonite clay to form, when hydrated, a barrier layer substantially impermeable to water.

After the application of polymer 108, additional steps may be taken to further enhance erosion-resistance. In the embodiment illustrated in FIG. 2, system 100 includes a user 104 utilizing an application device 206 to apply a slurry 220 to a surface 110 of earthen pit 102 covered by polymer 108. System 100 also includes water-resistant layer 222, cement 224, water 226, water softeners 228, agitator 230, and pump 232.

User 104 may be any suitable person, robot, or machine that utilizes application device 206 to apply slurry 220 to surface 110 covered by polymer 108. Application device 206, in the illustrated embodiment, is preferably a suitable hose with a nozzle at its end that is coupled to pump 232 in order to apply slurry 220 to surface 110 covered by polymer 108. Application device 206 may be other suitable devices for applying slurry 220 to surface 110 covered by polymer 108.

User 104 may apply slurry 220 with any suitable pressure to any suitable depth. For example, slurry 220 may be applied at high pressure to surface 110 at a depth of at least approximately one-quarter inch. In a more particular embodiment of the invention, slurry 220 is applied at high pressure to surface 110 at a depth of between approximately one-quarter and approximately one-half inches.

Slurry 220 is any suitable, somewhat viscous mixture capable of forming a layer substantially impermeable to water. In one embodiment of the invention, slurry 220 comprises a mixture of cement 224 and water 226. In a more particular embodiment of the invention, slurry 220 is a mixture of cement 224 and water 226 in a ratio of approximately one gallon of water 226 to approximately one pound of cement 224. Any suitable type of water 226 is contemplated by the various described embodiments; however, in a preferred embodiment, the water 226 is combined with water softeners 228, such as potash, to lower the pH of the water before combining water 226 with cement 224 to form slurry 220.

The application of slurry 220 to surface 110 covered by polymer 108 may be performed in any suitable manner. For example, slurry 220 may be applied to any portion of surface 110 covered by polymer 108. In the illustrated embodiment, agitator 230 agitates slurry 220 continuously while user 104 applies slurry 220 to cover an upper portion 238 of the walls 218 and a portion of the exterior rim 236 of earthen pit 102.

It should be noted that the slurry can be applied to surfaces that are or are not covered with the polymer, the bentonite (described further below), the water-resistant layer (described further below), or any other materials. In at least one embodiment, polymer is applied to a bottom portion and lower wall portions of a pit. The slurry is applied to upper-wall portions of the pit. The slurry forms a concrete barrier on the upper wall portions, for example, where wave action of fluids in the pit could otherwise cause erosion of the earthen upper wall portions. The lower wall portions and bottom portion of the pit (i.e., covered with polymer) may be further covered with bentonite to form, when hydrated, a substantially fluid impermeable layer. This may take the form, for example, of a gelatinous layer that prevents the transfer of fluids from one side of the layer to the other. It should be noted that various materials described herein may slightly overlap with one another even in embodiments where the materials are kept substantially separate.

To prevent greater erosion from the placement of an external object (not illustrated) into earthen pit 102, a water-resistant layer 222 may be anchored to a portion of the walls 218 covered by polymer 108. The external object may be any object purposefully placed on a portion of surface 110 for an extended time. For example, the external object may be a hose used temporarily or permanently to fill, drain, or otherwise maintain the contents (not illustrated) of earthen pit 102.

Utilization of the external object may require additional protection against erosion and fluid leakage. One embodiment of the present invention utilizes water-resistant layer 222 to further the erosion-reducing and leakage-reducing capabilities of the invention. Water-resistant layer 222 is any suitable material capable of substantially resisting water absorption. In one embodiment of the invention, water-resistant layer 222 is a plastic tarpaulin.

The application of water-resistant layer 222 may be performed in any suitable manner. For example, in one embodiment of the invention, the water-resistant layer 222 is anchored, from the bottom 114 to exterior rim 236 of earthen pit 102, by anchoring process generally used in the drilling jet industry.

In addition, the application of slurry 220 to water-resistant layer 222 may be performed in any suitable manner. For example, in one embodiment of the invention, user 104 applies slurry 220 to cover substantially all of water-resistant layer 222. In a preferred embodiment, user 104 utilizes application device 206 to apply slurry 220 to substantially cover an upper portion 238 of walls 218, a portion of the exterior rim 236, and substantially all of water-resistant layer 222.

In the embodiment illustrated in FIG. 3, system 100 includes a user 104 utilizing an application device 306 to apply bentonite 312 to a surface 110 covered by polymer 108. The present invention contemplates more, fewer, or different component for system 100 than those illustrated in FIG. 3.

User 104 may be any suitable person, robot, or machine that utilizes application device 306 to apply bentonite 312 to surface 110 covered by polymer 108. Application device 306, in the illustrated embodiment, is a mechanized applicator capable of applying bentonite 312. Application device 106 may be other suitable devices for applying bentonite 312 to surface 110.

User 104 may apply bentonite 312 at any suitable depth. For example, bentonite 312 may be applied to surface 110 covered with polymer 108 at a depth of at least approximately one-half inch. In a more particular embodiment of the invention, bentonite 312 is applied to surface 110 at a depth of approximately one-quarter inch to approximately three-quarters of an inch.

The application of bentonite 312 to surface 110 may be performed in any suitable manner. For example, in one embodiment of the invention, user 104 applies bentonite 312 to cover all interior surfaces 110 of earthen pit 102 covered by polymer 108. Any suitable dispersion of bentonite 312 (including partial dispersion) is contemplated by the present invention; however, in a preferred embodiment, bentonite 312 is applied to all surfaces 110 of earthen pit 102 covered by polymer 108, but not covered by slurry 320 or water-resistant layer 322, including bottom 314 and lower portion 316 of walls 318 of earthen pit 102.

Bentonite 112 is any suitable composition of bentonite clay adapted to combine with polymer 108 to form, when hydrated, a barrier layer substantially impermeable to water. Any suitable bentonite clay particles are contemplated by the present invention, such as dry clay particles. 

1. A method of lining an earthen formation, comprising: applying a polymer to at least a portion of the earthen formation; and applying bentonite to at least a portion of the earthen formation covered with the polymer, the bentonite adapted to combine with the polymer, when hydrated, to form a layer that is substantially impermeable to water.
 2. The method of claim 1, wherein applying the polymer comprises applying the polymer at a concentration of between approximately one-tenth and approximately two-tenths of a pound of the polymer per square foot of covered surface.
 3. The method of claim 1, wherein the polymer is applied in dry, granular form.
 4. The method of claim 1, wherein applying the polymer comprises applying the polymer to a bottom portion of the earthen formation.
 5. The method of claim 1, wherein applying the polymer comprises applying the polymer to the bottom portion and a lower wall portion of the earthen formation.
 6. The method of claim 1, wherein applying the polymer to at least a portion of the earthen formation comprises applying the polymer to all interior surfaces of the earthen formation, and to a portion of an exterior rim of the earthen formation.
 7. The method of claim 1, wherein applying bentonite clay comprises applying bentonite powder at a depth of at least approximately one-half inch.
 8. The method of claim 1, further comprising applying a protective slurry to at least a portion of the earthen formation covered with the polymer.
 9. The method of claim 8, wherein the protective slurry comprises a slurry of cement and water.
 10. The method of claim 8, wherein the protective slurry comprises a slurry of cement and water in a mixture in the ratio of approximately one pound of cement to approximately one gallon of water.
 11. The method of claim 8, wherein the protective slurry comprises a slurry of cement and water, the water having a reduced pH.
 12. The method of claim 11, wherein the pH is reduced by adding potash.
 13. The method of claim 8, wherein applying the protective slurry comprises applying the slurry at a depth of between approximately one-fourth and approximately one-half inch.
 14. The method of claim 1, further comprising applying a water-resistant layer to a portion of the earthen formation.
 15. The method of claim 14, wherein applying the protective slurry comprises applying the slurry to cover at least a portion of the water-resistant layer.
 16. A system for lining an earthen formation, comprising: a polymer; an application device operable to apply the polymer to a portion of a surface of the earthen formation; bentonite clay; and an application device operable to apply the bentonite clay to a portion of a surface of the earthen formation to form, when hydrated and combined with the polymer, a layer substantially impermeable to water.
 17. The system of claim 16, further comprising: a protective slurry; an application device operable to apply the protective slurry to a portion of a surface of the earthen formation.
 18. The system of claim 17, wherein the protective slurry comprises a mixture of at least cement and water.
 19. The system of claim 18, wherein the mixture of cement and water comprises a mixture in the ratio of approximately one pound of cement to approximately one gallon of water.
 20. The system of claim 18, wherein the mixture of cement and water comprises a mixture containing water with a reduced pH.
 21. The system of claim 16, further comprising a water-resistant layer applied to at least a portion of the earthen formation.
 22. The system of claim 21, wherein at least a portion of the water-resistant layer is covered by the protective slurry. 